feat: add WeChat QR code login and AGP WebSocket channel plugin

- Auth module: WeChat OAuth2 scan-to-login flow with terminal QR code
- Token persistence to ~/.openclaw/wechat-access-auth.json (chmod 600)
- Token resolution: config > saved state > interactive login
- Invite code verification (configurable bypass)
- Production/test environment support
- AGP WebSocket client with heartbeat, reconnect, wake detection
- Message handler: Agent dispatch with streaming text and tool calls
- Random device GUID generation (persisted, no real machine ID)

auth/utils.ts

@@ -0,0 +1,14 @@
+/**
+ * @file utils.ts
+ * @description 认证模块共享工具函数
+ */
+
+/** 安全嵌套取值 */
+export const nested = (obj: unknown, ...keys: string[]): unknown => {
+  let current = obj;
+  for (const key of keys) {
+    if (current == null || typeof current !== "object") return undefined;
+    current = (current as Record<string, unknown>)[key];
+  }
+  return current;
+};